> For the complete documentation index, see [llms.txt](https://docs.scaleflex.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.scaleflex.com/dynamic-media-optimization-dmo/settings/delivery/security.md).

# Security

## External domain whitelisting:

You can whitelist specific domains in order to allow only specific external sources to be requested. In addition, you can combine Domain whitelisting with Aliases to send custom headers to a non-public external storage for authentication purposes.

In order to set the whitelisting configuration for a specific domain, you need to have an Owner, Admin, Manager or Developer [User Role](/vxp-visual-experience-platform/settings/organisation/users/users.md#user-role) and to go to Settings > Optimization > Delivery > (tab) Security.

Then click on `+ Add domain` and enter the domain name that you would like to whitelist without the https\://- part:

<figure><img src="/files/5c6JfVwfYTu2QGVkmQCH" alt=""><figcaption></figcaption></figure>

In the example above, domain `sample.li` is whitelisted. Which means that if we try to process an image with any other domain except `sample.li`(eg: [www.your-own-domain.com](http://www.your-own-domain.com)), the system will return an error status code 406 (Not Acceptable).

If you prefer, this response can be changed to HTTP 404 (Default missing image).

<figure><img src="/files/hH8wiICzxYPp9oeBYatY" alt=""><figcaption></figcaption></figure>

Aliases are also supported. In case you have set a [Standard](/dynamic-media-optimization-dmo/settings/delivery/url-format.md#aliases) or a [Storage](/dynamic-media-optimization-dmo/settings/asset-origin.md) alias, you can add it as a value (eg: `_myalias_`) in the list of Whitelisted domains.


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